Physical inactivity is a growing health problem in the United States, especially for older people with chronic diseases such as COPD; in fact people with COPD are among the least active. Low levels of PA are associated with negative health outcomes including an increase in mortality and COPD exacerbations. Current PA guidelines focus on moderate-to-vigorous physical activities (MVPAs) that are too strenuous and not feasible for long term maintenance in many people with COPD. We propose a new paradigm for promoting physical activity (PA) in this population; focus on increasing time spent in light physical activity (LPA) and decreasing time spent in sedentary behavior. Growing evidence suggests that substantial health benefits are associated with increases in the volume of LPA. We propose to test the efficacy of our Active-for-Life (Active- Life) intervention and to quantify the mediating effects of potential mechanisms responsible for therapeutic outcomes. Our central hypothesis is that Active-Life will have positive effects on objectively measured PA. Active-Life is a 10 week intervention designed to increase total PA with an emphasis on increasing the time spent in LPA and decreasing sedentary time. Key components of Active-Life include (a) exercise with functional circuit training (FCT), walking and stretching in a laboratory-based exercise program that can easily be transitioned to the home setting with minimal equipment, (b) a behavioral component with a structured self- efficacy enhancing intervention that includes self-regulations strategies, (c) education that addresses the distinct health benefits of LPA and MVPA, the negative consequences of too much sedentary time, and an action plan for dealing with acute exacerbations of COPD and (d) follow-up with phone coaching and booster sessions. Active-Life establishes a goal for subjects, to increase total PA, combined LPA and MVPA, at least 60 minutes a day. This far exceeds the effects of other published PA interventions for people with COPD and if successful will advance PA science in clinically important ways. The Active-Life program was developed by Dr. Larson and through a series of preliminary studies; its feasibility is well established and preliminary data are promising. We propose to conduct a randomized controlled trial comparing Active-Life against an active control. We will enroll 183 people with moderate to very severe COPD. Outcomes will be measured at baseline, end of the 10 week intervention and at 3, 6 and 12 months after the end of the intervention. The primary dependent variables are objectively measured PA and sedentary behavior, measured with ActivPAL and Actigraph accelerometers simultaneously. Secondary outcome measures are indicators of frailty: 6-minute distance walk, isometric strength of knee flexors and extensors, Short Physical Performance Battery and self- reported physical function. Potential mediators include barriers-efficacy for PA and outcome expectations for PA. Innovations include the focus on LPA, objective measures of PA 24/7 and the use of FCT in COPD. This application is in response to NIH FOA PA-14-344 self-management for health with chronic conditions.